Conventionally, there is layout design using a sub-resolution assist feature (SRAF) as a method of improving a lithography margin of an exposure pattern (main pattern) in a semiconductor lithography technology.
As a method of arranging such SRAF, there are two technologies, which are a rule based SRAF to make an arrangement rule of the SRAF as a rule to arrange the SRAF according to the rule around the main pattern and a model based SRAF for arranging the SRAF for the main pattern using a certain model.
When arranging the SRAF around the main pattern, it is desired to arrange the SRAF in a short time also for the main pattern including a layout pattern in which the SRAF arrangement is difficult.